The present invention relates to a system and a method of roll stabilization of vehicles, in particular motor vehicles, where a controlling arrangement having at least one sensor for detecting a roll quantity and at least one slewing drive arranged between the two halves of the front and/or rear vehicle stabilizer, producing an initial stress in the stabilizer halves to reduce or suppress the rolling motion and, in the event of a roll, applying a counter-torque to the vehicle body as a function of sensor output signals.
A system and method relating to roll stabilization of vehicles is generally described in Konstruktion und Elektronik, no. 17, page 9, Aug. 5, 1992.
With such a system, a counter-torque is applied to the body by a suitable adjustment spring to suppress the rolling motion of the vehicle body when turning a corner. This torque is preferably produced on the stabilizers of the front and rear axles. The conventional stabilizers designed as torsion bar springs are disconnected, and a slewing drive which can generate an active torsion and thus an initial stress of the stabilizer halves is arranged between the two stabilizer halves. With the help of such a system, both driving performance and driving comfort are improved, i.e., the rolling motion of the vehicle body is reduced or suppressed while the right and left sides of the vehicle are uncoupled in the event of one-sided roadway effects.
The known system mentioned above uses a hydraulic actuator. Such a hydraulic actuator needs special installations in the vehicle which are sometimes expensive, e.g., extensive pipework. Power is still expended even when driving in a straight line and in quasi-steady states of the vehicle, depending on the design of the pressure supply, so that no-load pump losses occur even when driving in a straight line. Hydraulic systems installed in a vehicle also have the disadvantage that hydraulic fluid which is an environmental pollutant can escape when there is a leak in the system, e.g., due to an accident.
In view of the preceding discussion, an object of the present invention is to make possible a purely electromechanical system design for roll stabilization that will yield a reduction in the required power in steady-state or quasi-steady-state driving maneuvers while also reducing costs in comparison with the known hydraulic designs.
Based on such an electromechanical system for roll stabilization according to the present invention, a method according to the present invention should make it possible to achieve a reduced rolling motion in comparison with a passive vehicle even outside the control range.
According to an aspect of the present invention, a generic system for roll stabilization of vehicles that achieves the object defined above is characterized in that the slewing drive is an electromechanical slewing drive and has an arrangement for locking swiveling of the stabilizer halves with respect to one another.
The roll stabilization system according to the present invention permits simple installation in the vehicle because it has a simple electromechanical control unit. Environmental safety and installation costs are improved in comparison with a hydraulic system. The roll stabilization system according to the present invention does not require any power when driving in a straight line because in that case there are no hydraulic pump losses.
Due to the preferred use of a brake that is applied or released electromagnetically for locking, it is possible to lower the required power in steady-state or quasi-steady-state driving maneuvers and to reduce the thermal load on the electric motor. When the brake is applied, overload protection is achieved, permitting slippage when the torque is too high and thus protecting the parts.
Furthermore, the electromechanical slewing drives mounted on the front and rear axles also permit a reduction in the rolling motion above the controllable torques when the brake is applied.
Use of brakes that are applied or released electromagnetically depends on the system failure strategy employed. With brakes that are applied electromagnetically, the stabilizer halves on the front and rear axles are separated in a system failure. The rolling behavior and self-steering behavior are thus determined only by the conventional spring and shock absorber elements.
With electromagnetically released brakes, suitable measures must that the electromechanical actuator on the front and rear axles can be locked only in the middle position in a system failure to prevent inclination of the vehicle body in driving in a straight line. The stabilizer halves locked with respect to one another in this way then act like passive torsion bar springs. The rolling and self-steering behavior are determined through the choice of torsional rigidity.
An additional improvement in comfort can be achieved by using a clutch between the drive end and the output end of the actuator. Depending on the arrangement of the clutch, the electric motor and/or the gear or individual gear stages can be separated from the output end of the control unit, and the decoupling of the right and left sides of the vehicle can be improved by the resulting reduction in the moments of inertia. Depending on the design, a separate brake and/or clutch or a corresponding brake-clutch combination may be used.
A transverse acceleration sensor may be used to advantage as a sensor to detect a roll parameter of the vehicle. In addition, a sensor may also be provided to detect the steering wheel angle and another sensor may be provided to detect the vehicle speed.
The sensor(s), the electromechanical actuator and the brakes are advantageously each connected to an electronic control unit to generate corresponding control signals for the electromechanical slewing drive and the brakes as a function of the signals delivered by the sensors with the help of preset algorithms or learning algorithms executed in the electronic control unit.
The method using the roll stabilization system according to the present invention for roll stabilization of vehicles is characterized by the following steps:
I. Determining the maximum settable torque from the parameters:
maximum motor torque of the electric slewing motor,
gear reduction,
efficiency and
torque loss;
II. Determining the required actuating torque;
III. Releasing the brake and applying the torque to the low-torque end of the slewing motor when the required actuating torque is below the maximum actuating torque;
IV. Applying the brake when the required actuating torque exceeds the maximum actuating torque of the slewing drive, and
V. Generating setpoint currents for the electric motors to generate a counter-torque for roll stabilization.
The roll stabilization system according to the present invention can also be used for certain leveling and inclination effects of the vehicle body when the vehicle is stationary and for raising and lowering individual wheels. The following applications can be implemented in particular:
Manual or automatic leveling of a vehicle about its longitudinal axis by suitably energizing the slewing drives and locking by applying the brakes, e.g., a vehicle standing on a slope or a camper trailer or the like standing on a curb at one side;
Manual or automatic leveling of a vehicle about its longitudinal axis when the vehicle is standing with a single wheel in a depression;
Use of the roll stabilization system as an entry or exit aid with facilitated opening and closing of the door due to a certain inclination of the vehicle body;
Use of the roll stabilization system for simpler loading of a roof luggage rack, a bicycle rack, etc. by inclining the body while the longitudinal axis remains horizontal;
Use of the roll stabilization system for lifting individual wheels, e.g., for changing a tire, by diagonal displacement of the front and rear slewing drives;
Use of the roll stabilization system for a defined inclination of the vehicle body or for lifting individual wheels through appropriately energizing the slewing drives and then locking the brakes, e.g., so that objects beneath the vehicle can be removed more easily or to create accessibility to the underbody of the vehicle, e.g., for repair work.